1. Field of the Invention
The present invention relates to automatic cutting condition changeover equipment which automatically changes the electrical cutting condition of a wire-cut, electric discharge machine in accordance with the thickness of the workpiece.
2. Description of the Prior Art
A wire-cut, electric discharge machine cannot achieve optimum cutting of the workpiece unless an electrical cutting conditions of the machine, which depend on the peak current Ip or the no-load voltage Vs of the power source or on the ON time .tau..sub.on and OFF time .tau..sub.off of a pulse current is changed sharply in accordance with the thickness of the workpiece. For example, in the case of the peak current Ip being not varied in accordance with the work piece thickness if a workpiece of small thickness is cut under the same conditions as those for a workpiece of large thickness, then a wire electrode will be broken; conversely, if the thick workpiece is cut under the same conditions as those for the thin workpiece, then a sufficient cutting speed will not be obtained. But manually changing the electrically cutting conditions for each particular workpiece is very troublesome to the operator and, further, complicates continuous, fully automatic cutting of a workpiece of uneven thickness. To solve such problems, there has already been proposed and put to practical use automatic cutting condition change-over equipment which is capable of automatically changing over the electrical cutting condition in response to variations in the thickness of a workpiece during cutting.
According to the conventional automatic cutting condition changeover equipment, for instance, cutting speeds corresponding to selected values of the peak current Ip and the optimum cutting condition are prestored in an electronic computer for each workpiece thickness. The thickness of a workpiece to be cut is estimated from an actual cutting speed and cutting condition through the use of the computer and compared with the prestored optimum cutting condition and then the peak current Ip is changed over to an optimum value. However, this prior art equipment requires, in addition to the use of an electronic computer, a large number of experiments for obtaining the data to be prestored in the computer; furthermore, since all the data thus obtained must be prestored, their processing is very troublesome.